[ios] Add MGLMapView.showsScale to control scale bar visibility (#11335)

- Fixes scale bar not being visible until a camera change event.
- Adds IBInspectable for scale bar visibility.
- Add tests of the scale bar being added to the map view

2 files changed, 65 insertions, 2 deletions

diff --git a/platform/ios/test/MGLMapViewLayoutTests.m b/platform/ios/test/MGLMapViewLayoutTests.m
index e707cfdb41..16f6cdada3 100644
--- a/platform/ios/test/MGLMapViewLayoutTests.m
+++ b/platform/ios/test/MGLMapViewLayoutTests.m
@@ -37,14 +37,15 @@
     self.styleLoadingExpectation = [self expectationWithDescription:@"Map view should finish loading style."];
     [self waitForExpectationsWithTimeout:1 handler:nil];
 
+    self.mapView.showsScale = YES;
+
     //set zoom and heading so that scale bar and compass will be shown
-    [self.mapView setZoomLevel:4.5 animated:NO];
+    [self.mapView setZoomLevel:10.0 animated:NO];
     [self.mapView.camera setHeading:12.0];
 
     //invoke layout
     [self.superView setNeedsLayout];
     [self.superView layoutIfNeeded];
-
 }
 
 - (void)mapView:(MGLMapView *)mapView didFinishLoadingStyle:(MGLStyle *)style {
diff --git a/platform/ios/test/MGLMapViewScaleBarTests.m b/platform/ios/test/MGLMapViewScaleBarTests.m
new file mode 100644
index 0000000000..11d1187263
--- /dev/null
+++ b/platform/ios/test/MGLMapViewScaleBarTests.m
@@ -0,0 +1,62 @@
+#import <Mapbox/Mapbox.h>
+#import <XCTest/XCTest.h>
+
+@interface MGLMapViewScaleBarTests : XCTestCase
+
+@property (nonatomic) MGLMapView *mapView;
+
+@end
+
+@implementation MGLMapViewScaleBarTests
+
+- (void)setUp {
+    [super setUp];
+
+    [MGLAccountManager setAccessToken:@"pk.feedcafedeadbeefbadebede"];
+    NSURL *styleURL = [[NSBundle bundleForClass:[self class]] URLForResource:@"one-liner" withExtension:@"json"];
+    self.mapView = [[MGLMapView alloc] initWithFrame:UIScreen.mainScreen.bounds styleURL:styleURL];
+}
+
+- (void)tearDown {
+    self.mapView = nil;
+
+    [super tearDown];
+}
+
+- (void)testShowsScale {
+    UIView *scaleBar = self.mapView.scaleBar;
+
+    // Scale bar should not be enabled by default.
+    XCTAssertFalse(self.mapView.showsScale);
+    XCTAssertTrue(scaleBar.hidden);
+
+    self.mapView.showsScale = YES;
+
+    XCTAssertFalse(scaleBar.hidden);
+
+    // Scale bar should not be visible at default zoom (~z0), but it should be ready.
+    XCTAssertFalse(CGRectIsEmpty(scaleBar.frame));
+    XCTAssertEqual(scaleBar.alpha, 0);
+
+    self.mapView.zoomLevel = 15;
+    XCTAssertGreaterThan(scaleBar.alpha, 0);
+}
+
+- (void)testDirectlySettingScaleBarViewHiddenProperty {
+    UIView *scaleBar = self.mapView.scaleBar;
+
+    scaleBar.hidden = NO;
+    XCTAssertFalse(scaleBar.hidden);
+
+    // Directly setting `.hidden` after the map has finished initializing will not update the scale bar.
+    XCTAssertTrue(CGRectIsEmpty(scaleBar.frame));
+
+    // ... but triggering any camera event will update it.
+    self.mapView.zoomLevel = 1;
+    XCTAssertFalse(CGRectIsEmpty(scaleBar.frame));
+    XCTAssertEqual(scaleBar.alpha, 0);
+
+    self.mapView.zoomLevel = 15;
+    XCTAssertGreaterThan(scaleBar.alpha, 0);
+}
+@end